Tsarin Sarrafa Lantarki Mai Rukuni na LED-Hudu da LED-Biyu don Sadarwar Haske da ake iya Gani

1. Gabatarwa & Bayyani

Sadarwar Haske da ake iya Gani (VLC) tana amfani da Fitilun LED don haskakawa da watsa bayanai a lokaci guda. Kalubale mafi mahimmanci shine samar da siginoni masu kyau, masu ƙima na gaske waɗanda suka dace da ƙarfin sarrafa ƙarfin LED, musamman lokacin amfani da sarrafa lantarki mai sarkakiya kamar QAM tare da OFDM. Hanyoyin VLC-OFDM na gargajiya (misali, DCO-OFDM, ACO-OFDM) suna sanya daidaiton Hermitian akan vector alamar yanki mai mita kafin Juyawar Fourier Mai Sauri (IFFT). Wannan yana tabbatar da siginar lokaci mai ƙima na gaske amma yana rage ingancin yanki da rabi, kamar yadda $N$ ƙananan masu ɗaukar kaya ke ɗaukar alamu masu sarkakiya $N/2$ kawai.

Wannan takarda ta Narasimhan et al. ta gabatar da sauyin tsari: ƙetare ƙayyadaddun daidaiton Hermitian ta hanyar amfani da sararin samaniya ta amfani da LED da yawa. Babban ra'ayi shine raba watsa abubuwan (na gaske/na hasashe ko girma/lokaci) na alama mai sarkakiya a cikin LED daban-daban. Wannan aikin ya gabatar da sabbin tsare-tsare guda uku: Tsarin Sarrafa Lantarki Mai Rukuni na LED-Hudu (QCM), Tsarin Sarrafa Lantarki Mai Rukuni na LED-Biyu (DCM), da Tsarin Sarrafa Lantarki Mai Rukuni na Sararin Samaniya DCM (SM-DCM).

2. Tsare-tsaren Sarrafa Lantarki da aka Gabatar

2.1 Tsarin Sarrafa Lantarki Mai Rukuni na LED-Hudu (QCM)

QCM yana amfani da LED huɗu don watsa alama mai sarkakiya ɗaya $s = s_I + j s_Q$.

• Rarraba Girma da Alama: Ƙimar cikakkiyar $|s_I|$ da $|s_Q|$ ana isar da su ta hanyar ƙarfin haske (ikon gani) na keɓaɓɓun LED guda biyu.
• Ƙididdigar Sararin Samaniya don Alama: Alamun $s_I$ da $s_Q$ ana isar da su ta hanyar kunna takamaiman nau'i-nau'i na LED daga cikin huɗu. Misali, kunna takamaiman nau'i-nau'i na LED na iya wakiltar $(+ , +)$, wani kuma $(+ , -)$, da sauransu.

Wannan ya raba bayanan girma da alama, yana ba da damar amfani da sauƙaƙan sarrafa ƙarfin haske, mai kyau koyaushe don LED masu ɗaukar girma.

2.2 Tsarin Sarrafa Lantarki Mai Rukuni na LED-Biyu (DCM)

DCM tsari ne mai ingancin yanki mafi girma wanda ke amfani da LED biyu kawai. Yana amfani da wakilcin polar na alama mai sarkakiya $s = r e^{j\theta}$.

• LED 1 (Girma): Yana watsa girman $r$ ta hanyar sarrafa ƙarfin haske.
• LED 2 (Lokaci): Yana watsa lokacin $\theta$ ta hanyar sarrafa ƙarfin haske. Wannan yana buƙatar sassaka ƙimar lokaci $\theta \in [0, 2\pi)$ zuwa matakin ƙarfin haske mai kyau, misali, ta amfani da $\cos(\theta)$ ko takamaiman aikin sassakawa.

DCM yana cimma ingancin yanki iri ɗaya kamar tsarin sarrafa lantarki mai sarkakiya na gargajiya ba tare da nauyin daidaiton Hermitian ba.

2.3 Tsarin Sarrafa Lantarki Mai Rukuni na Sararin Samaniya DCM (SM-DCM)

SM-DCM yana haɗa manufar Sarrafa Sararin Samaniya (SM) tare da DCM don haɓaka ƙimar bayanai ko ƙarfi.

• Tsari: Ana amfani da tubalan DCM guda biyu, kowanne yana ɗauke da LED biyu (jimlar LED 4).
• Aiki: Ƙarin "bit na fihirisa" yana zaɓar ko wanne daga cikin tubalan DCM guda biyu yake aiki a cikin amfani da tashar da aka ba. Sa'an nan kuma tubalin da ke aiki yana watsa alama mai sarkakiya ta amfani da ka'idar DCM ta yau da kullun.

Wannan yana ƙara ƙarin bit ɗaya kowace amfani da tashar (bit na sararin samaniya) idan aka kwatanta da DCM na asali, yana ƙara ƙimar bayanai.

3. Cikakkun Bayanai na Fasaha & Tsarin Tsarin

3.1 Tsarin Lissafi

Siginar da aka karɓa vector $\mathbf{y}$ don tsarin da ke da LED $N_t$ da ƙwayoyin hoto (PDs) $N_r$ shine: $$\mathbf{y} = \mathbf{H} \mathbf{x} + \mathbf{n}$$ inda $\mathbf{H}$ shine matrix tashar VLC $N_r \times N_t$ (mai kyau, ƙima ta gaske saboda sarrafa ƙarfin haske/gane kai tsaye), $\mathbf{x}$ shine vector ƙarfin da aka watsa $N_t \times 1$ (ba mara kyau ba), kuma $\mathbf{n}$ shine ƙara farar Gaussian amo.

Don DCM yana watsa alamar $s=r e^{j\theta}$, tare da LED 1 da 2 da aka sanya su ga girma da lokaci bi da bi, vector watsawa zai iya zama: $$\mathbf{x} = \begin{bmatrix} r \\ f(\theta) \end{bmatrix}$$ inda $f(\cdot)$ aiki ne da ke sassaka lokaci zuwa ƙarfin haske mai kyau, misali, $f(\theta) = \alpha (1+\cos(\theta))$ tare da $\alpha$ yana tabbatar da rashin kyau.

3.2 Ƙirar Mai Gano

Takardar ta gabatar da masu gano guda biyu don tsarin QCM/DCM-OFDM:

1. Mai Gano Sifili-Zaɓi (ZF): Mai gano layi wanda ke juyar da tashar: $\hat{\mathbf{s}} = \mathbf{H}^{\dagger} \mathbf{y}$, inda $\dagger$ ke nuna pseudo-juzu'i. Mai sauƙi amma yana iya ƙara amo.
2. Mai Gano Mafi Ƙaramin Nisa (MD): Mai gano mara layi, mafi kyau (a ma'anar ML don AWGN) wanda ke gano vector alamar da aka watsa wanda ke rage nisan Euclidean: $$\hat{\mathbf{x}} = \arg\min_{\mathbf{x} \in \mathcal{X}} \| \mathbf{y} - \mathbf{H}\mathbf{x} \|^2$$ inda $\mathcal{X}$ shine saitin duk yuwuwar vector ƙarfin haske da aka watsa don tsarin sarrafa lantarki.

4. Nazarin Aiki & Sakamako

4.1 Aikin BER & Iyakoki

Takardar ta samo ƙaƙƙarfan iyakoki na sama na nazari don Ƙimar Kuskuren Bit (BER) na tsare-tsaren QCM, DCM, da SM-DCM. Simintin gwaji ya tabbatar da waɗannan iyakokin. Babban binciken:

• DCM ya fi QCM don ingancin yanki iri ɗaya saboda yana amfani da makamashi yadda ya kamata ta hanyar keɓance LED zuwa girma da lokaci kai tsaye, maimakon raba sassan gaske/hasashe da alamunsu.
• SM-DCM yana ba da ciniki mai kyau, yana ba da ƙimar bayanai mafi girma fiye da DCM (saboda bit na fihirisa na sararin samaniya) yayin da yake kiyaye mafi kyawun aikin BER fiye da QCM a ƙimar kwatankwacinsa.
• Mai gano MD ya fi mai gano ZF sosai, musamman a cikin ƙananan yanayin SNR ko tashoshin MIMO marasa kyau.

4.2 Ƙirar Ƙimar da ake iya Samu

Gudunmawa mai mahimmanci shine nazarin ƙirar ƙimar da ake iya samu don manufar BER. Maimakon kawai iya aiki mai girma, marubutan sun zana rarraba sararin samaniya na ƙimar da ake iya samu (bit/amfani da tashar) a cikin tsarin ɗaki don ƙayyadaddun manufar BER (misali, $10^{-3}$).

• Hangen Nesa: Waɗannan ƙirar suna nuna yankuna a cikin ɗaki inda takamaiman tsarin sarrafa lantarki (QCM, DCM, SM-DCM) zai iya cimma takamaiman ƙimar bayanai cikin aminci.
• Hankali: DCM da SM-DCM gabaɗaya suna nuna yankuna masu ƙimar girma idan aka kwatanta da QCM, suna nuna mafi kyawun aikin su da ɗaukar hoto.

Wannan kayan aikin nazari na aiki yana da mahimmanci don ƙirar tsarin VLC da tsara shigar da shi.

5. Hangen Nesa na Manazarcin: Babban Hankali & Zargi

Babban Hankali: Aikin Narasimhan et al. wata wayo ce, mai sane da kayan aiki wacce ta sake tunani game da matsalar samar da siginar "sarkakiya-zuwa-gaske" a cikin VLC. Maimakon magance ta a cikin yankin lambobi tare da daidaiton Hermitian—hanya mai kama da asarar daidaiton zagayawa a cikin CycleGAN (Zhu et al., 2017) wanda ke tilasta ƙayyadaddun tsarin a cikin bayanai—suna jujjuya shi zuwa bambancin sararin samaniya na Layer na zahiri. Wannan yana tunawa da yadda RF Massive MIMO ke amfani da digiri na 'yanci na sararin samaniya don haɗawa, amma a nan ana amfani da shi don rushewar tauraro. Haƙiƙanin ƙirƙira shine gane cewa babban rawar da jerin LED ke takawa a cikin VLC ba kawai haɗawa ta MIMO ba ne; zai iya zama mai zana tauraro.

Kwararar Ma'ana: Ma'anar takardar ba ta da tabbas: 1) Gano toshewar (nauyin daidaiton Hermitian). 2) Gabatar da ka'idar rushewar sararin samaniya (QCM). 3) Inganta don inganci (DCM). 4) Haɗa ƙarin girma na haɗawa (SM-DCM). 5) Tabbatar da shi tare da cikakken bincike (iyakokin BER, ƙirar ƙima). Wannan misali ne na littafi na ci gaba na bincike mai ƙima amma mai ma'ana.

Ƙarfi & Kurakurai: Ƙarfi: Kyakkyawan ra'ayi yana da girma. Ingantaccen ingancin yanki na DCM shine fasalin kashe shi. Nazarin ƙirar ƙima ya fice, yana motsawa bayan lankwasa SNR/BER na ka'idar zuwa ma'auni na shigar da aiki, yana daidaitawa tare da yanayin a cikin rahotannin IEEE da ITU-R kan tsarin tsarin VLC. Guje wa son zuciya na DC ko yanke (gama gari a cikin DCO/ACO-OFDM) yana sauƙaƙe ƙirar mai watsawa. Kurakurai: Giwa a cikin ɗaki shine buƙatar bayanin yanayin tashar (CSI). Aikin MD har ma da masu gano ZF yana raguwa sosai tare da CSI mara kyau, babban kalubale a cikin yanayin VLC na aiki, mai motsi tare da motsi na mai amfani da inuwa. Nazarin takardar yana ɗauka cikakken CSI. Bugu da ƙari, sassakawar lokaci-zuwa-ƙarfin haske $f(\theta)$ a cikin DCM ba layi ne kuma yana iya zama mai hankali ga rashin layi na LED. Idan aka kwatanta da ƙarin ayyukan kwanan nan akan sassakawar fihirisa ko masu karɓa na hanyar sadarwar jijiya don VLC (kamar yadda aka gani a cikin ƙaddamarwar arXiv daga baya), sarrafa siginar a nan yana da al'ada.

Hankali mai Aiki: Ga masu aiki a masana'antu: 1. Fara fifita DCM akan QCM don sabbin ƙira; ribar ingancin LED 2x tana da girma. 2. Yi amfani da hanyar ƙirar ƙima daga wannan takarda don tsara wurin zafi na VLC na ainihi (misali, a ofisoshi, gidajen tarihi). 3. Yi la'akari da tsammanin CSI a matsayin babban haɗari. Zuba jari a cikin ingantattun dabarun ƙididdiga na tashar ko kuma yi la'akari da bambance-bambancen ɓoyayyen DCM don rage wannan. 4. Bincika tsare-tsaren gauraye: Yi amfani da DCM don tsayayyen hanyoyin haɗin gwiwa masu ƙimar girma, kuma komawa zuwa ƙarin ƙarfi, sauƙaƙan sarrafa lantarki (kamar OOK) don masu amfani na wayar hannu. Aikin yana ba da kayan aiki mai ƙarfi, amma haɗa shi cikin cikakken tsari, mai ƙarfi yana buƙatar magance kalubalen ƙididdiga na tashar na aiki kai tsaye.

6. Tsarin Nazari & Misalin Shari'a

Tsari: Kwatanta Aiki a Ƙarƙashin CSI mara Kyau

Yanayi: Kimanta QCM, DCM, da SM-DCM a cikin ɗaki 4m x 4m x 3m tare da LED 4 da aka ɗora a rufi (an shirya su a cikin murabba'i) da mai karɓar PD guda ɗaya a tsayin tebur. Manufar ita ce kiyaye mafi ƙarancin ƙimar bit 2/amfani da tashar a BER na $10^{-3}$.

Matakai:

1. Ƙirar Tashar: Yi amfani da tsarin tashar VLC na gargajiya: $h = \frac{(m+1)A}{2\pi d^2} \cos^m(\phi) T_s(\psi) g(\psi) \cos(\psi)$ don LOS, inda $m$ shine tsari na Lambertian, $d$ nisa, $\phi$ kusurwar haskakawa, $\psi$ kusurwar faruwa, $T_s$, $g$ tacewar gani da ribar mai tattarawa.
2. CSI mara Kyau: Ƙirar tashar da aka ƙiyasta $\hat{\mathbf{H}} = \mathbf{H} + \mathbf{E}$, inda $\mathbf{E}$ matrix kuskure ne tare da abubuwa i.i.d. Gaussian, bambanci daidai da SNR$^{-1}$.
3. Nazari:
   • Lissafa ƙaƙƙarfan iyaka na sama na BER na ka'idar (daga takardar) don cikakken CSI a SNR daban-daban da wurare.
   • Yi simintin gwaji na mai gano MD ta amfani da $\hat{\mathbf{H}}$ mara kyau kuma lura da hukuncin SNR da ake buƙata don kiyaye manufar BER.
   • Zana ragewa na ƙirar ƙimar da ake iya samu (don manufar BER) lokacin da bambancin kuskuren CSI ya karu daga 0% zuwa 10%.
4. Hankalin da ake tsammani: SM-DCM, tare da zaɓin sararin samaniya na asali, na iya nuna ƙarin ƙarfi ga kurakuran ƙididdiga na tashar a wasu wurare idan aka kwatanta da DCM, kamar yadda gano fihirisa zai iya zama ƙasa da hankali ga ƙananan kurakuran girman tashar fiye da daidaitaccen gano girman/lokaci na DCM.

Wannan shari'ar ta ƙaddamar da nazarin cikakken CSI na takardar zuwa girma mai mahimmanci na aiki.

7. Aikace-aikacen Gaba & Jagorori

Ka'idojin QCM/DCM sun buɗe hanyoyi masu ban sha'awa da yawa:

• Li-Fi a cikin IoT na Masana'antu: Ƙarfi da ingancin DCM sun sa ya dace don hanyoyin haɗin gwiwa masu ƙimar bayanai masu girma, gajeren zango a cikin saitunan masana'antu (misali, sadarwar inji-zuwa-inji a cikin masana'antun sarrafa kai) inda tsangwama na RF ke da damuwa kuma matsayi suna da ƙayyadaddun ƙayyadaddun (rage matsalolin CSI).
• VLC na Ƙarƙashin Ruwa: Don sadarwar ƙarƙashin ruwa inda ake amfani da LED shuɗi-kore, tsarin mai watsawa mai sauƙi na DCM zai iya zama fa'ida. Bincike daga cibiyoyi kamar Cibiyar Nazarin Teku ta Woods Hole ya nuna buƙatar ingantaccen sarrafa lantarki a cikin tashoshi masu tsauri na ƙarƙashin ruwa.
• Haɗawa tare da Masu Karɓa na Ci-gaba: Aikin nan gaba ya kamata ya haɗa DCM tare da masu karɓa na tushen koyo mai zurfi (misali, masu gano CNN ko Transformer) waɗanda za su iya yin ƙididdiga na tashar tare da gano alama tare, yuwuwar cin nasara akan iyakacin cikakken CSI. Wannan yana daidaitawa tare da yanayin ƙaddamarwar arXiv akan koyon inji don sadarwa.
• Tsarin RF/VLC Gauraye: DCM zai iya zama ɓangaren saurin gudu mai girma, gajeren zango a cikin cibiyar sadarwa iri-iri, tare da RF yana ba da ɗaukar hoto da tallafin motsi. Nazarin ƙirar ƙima zai iya ba da labari kai tsaye irin wannan tsarin hanyar sadarwa gauraye.
• Daidaituwa: Ribar ingancin DCM tana ba da damar la'akari da haɗa shi cikin ƙa'idodin VLC na gaba ta ƙungiyoyi kamar IEEE 802.15.7. Kawar da daidaiton Hermitian fa'ida ce ta zahiri akan sassan PHY na tushen OFDM da ake da su.

8. Nassoshi

1. Narasimhan, T. L., Tejaswi, R., & Chockalingam, A. (2016). Quad-LED and Dual-LED Complex Modulation for Visible Light Communication. arXiv:1510.08805v3 [cs.IT].
2. Zhu, J.-Y., Park, T., Isola, P., & Efros, A. A. (2017). Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networks. Proceedings of the IEEE International Conference on Computer Vision (ICCV).
3. IEEE 802.15.7-2018: Standard for Local and Metropolitan Area Networks--Part 15.7: Short-Range Optical Wireless Communications.
4. ITU-R Reports on Visible Light Communication Systems.
5. Woods Hole Oceanographic Institution. (n.d.). Optical Communications. Retrieved from https://www.whoi.edu.
6. Mesleh, R., et al. (2008). Spatial Modulation. IEEE Transactions on Vehicular Technology.
7. Armstrong, J. (2009). OFDM for Optical Communications. Journal of Lightwave Technology.